Change Management and Configuration Management

Answer:
Configuration Items (CIs) that are within the scope of the plan are used by the Change Management process to evaluate and authorize changes. The Change Management process authorizes all changes on CIs which are within the scope of the SACM Plan.

So, while planning how to populate CMBD (which is in jurisdiction of Configuration management, or Service Asset and Configuration Management) you need to think about scope ("width" and "depth" of the implementation i.e. affected CI's), location, naming nomenclature, tools..etc. Once you define that i.e. have your plan ready, you can start the implementation. In scope of the planning you need to consider how (i.e. who, in which tool and with what authority) people involved in change Management will use information stored in CMDB.

Here are the article that may help:
"What is the role of the Service Asset and Conf iguration Manager according to ITIL/ISO 20000?" https://advisera.com/20000academy/blog/2016/11/01/what-is-the-role-of-the-service-asset-and-configuration-manager-according-to-itil-iso20000/
"How to use ITIL to prepare the Service Asset & Configuration Management Plan" https://advisera.com/20000academy/blog/2015/12/01/how-to-use-itil-to-prepare-the-service-asset-configuration-management-plan/
"Three main activities to set up ITIL Service Asset and Configuration Management" https://advisera.com/20000academy/blog/2015/07/14/three-main-activities-to-set-up-itil-service-asset-and-configuration-management/

as well as free webinar
"The basic elements of ITIL Service Asset and Configuration Management (SACM)" https://advisera.com/20000academy/webinar/the-basic-elements-of-itil-service-asset-and-configuration-management-sacm-free-webinar-on-demand/